Dispensing systems are known which comprise a pump provided with a tube for the pressurised supply of the product, on which a dispensing head of the pushbutton type is fixed in order to actuate the movement of said tube over a dispensing stroke and to actuate the suction of the product.
In particular, the dispensing head may comprise a body having a well for mounting said head on the supply tube and a product dispensing path. According to one embodiment, the dispensing path emerges in a dispensing space formed in a nozzle having a product discharge passage. Thus, by pressing on the body of the dispensing head, the pump is actuated in order to dispense the product through the discharge passage as a small amount or as a continuous stream.
Throughout the world, various directives aim to regulate, control or limit the presence of substances that are potentially hazardous for human health in products, in particular cosmetic products. One of them is the European Directive REACh (Registration Evaluation and Authorisation of Chemicals). Thus an environmental trend is pushing cosmetics manufacturers to limit, or even eliminate from the formulae, preservatives that are often the cause of allergies or intolerances.
Cosmetic products are therefore becoming more and more fragile. In particular, it is difficult for them to withstand mechanical or thermal stress (causing for example phase separation), contact with air (causing for example drying or oxidation), and are easily contaminated by bacteria, yeasts and moulds.
To combat such contaminations, formulators attempt to reinforce the intrinsic preservative activity of their products by adding ingredients having a preservative activity, such as certain essential oils, orange essences, vitamin C, etc., which are not declared as preservatives. Thus they limit the free activity of water, which they attempt to keep low (AW<0.6) so that bacteria do not develop or only develop a little. The standard NF 29621 describes such means. However, formulators quickly come up against the limits of such a strategy.
On the other hand, both with regard to the container in which the product is packaged and with regard to the dispensing head, protective bottles are appearing on the market. In particular, the bottles must prevent the microbiological contamination of the product, not only during storage but especially between two uses, and in particular by back contamination from the discharge passage towards the inside of the container through the dispensing space.
To do this, dispensing heads have been proposed where the discharge passage is equipped with a membrane that can be deformed by the product exerting pressure thereon, between a closed and open state of the discharge passage respectively. In particular, the impermeability of the closure between two dispensings can be achieved by pressing the flexible membrane on a rigid geometry.
However, this strategy finds its limit in the fact that it is impossible to obtain a sufficiently close pressing interface to prevent contaminants of very small sizes entering the dispensing space through said interface.
Furthermore, the membrane pressed in the discharge passage is in direct contact with the outside air, giving rise to a risk of rapid drying of the small quantity of product disposed at the sealing interface. Thus, between two uses, all the more so if relatively spaced apart in time, the membrane has a tendency to stick in the closed state, actuation of the dispensing causing a pressurisation of the product in the dispensing space to a sufficient level to cause detachment, then leading to an abrupt discharge of the product through the passage thus opened.